E-Mobility Engineering 019 | In conversation: Stephen Lambert l WAE EVR l Battery case materials focus l Quality control insight l Clipper Automotive Clipper Cab digest l Optimising battery chemistries insight l Powertrain testing focus

Some suppliers of battery pack materials Canada Targray +1 514 695 8095 www.targray.com China ADV Cooler +86 135 8426 7707 www.advcooler.com EMP Tech +86 180 2619 3705 www.empcasting.com Trumony Aluminium +86 1358 4862 808 www.trumony.com Germany Covestro +49 214 6009 2000 www.covestro.com Evonik Industries +49 201 17701 www.evonik.com Freudenberg Performance Materials +49 6201 800 www.freudenberg-pm.com Henkel +49 9 211 797 0 www.henkel.com SGL Carbon +49 611 60290 www.sglcarbon.com Thyssenkrupp Steel +49 203 52 24569 www.thyssenkrupp-steel.com Saudi Arabia SABIC +966 11 225 8000 www.sabic.com UK Steatite +44 1527 512400 www.steatite.com USA Teijin Automotive Technologies +1 248 237 7800 www.teijinautomotive.com 40 breakage in the cooling system and were looking for a material to absorb the glycol coolant. That project did not progress but it led to one that needed to maintain a 15- 40 oC temperature range with coolant while making sure there was no leakage. This was achieved with a non-woven material coated with superabsorbent particles. Depending on the humidity outside, the material becomes soft and so absorbs more water. Tests showed liquid absorbers can manage the humidity in a case by absorbing moisture and releasing it by drying it in a less humid environment. The standard alternative material for absorbing water in a battery pack is silica gel. This dries the air but is hygroscopic, so there is a diffusion of humidity and it does not redry. It needs a temperature of 80 oC or humidity below 20% to release the captured moisture. Silica gel also needs to be replaced about every 2 years as part of the regular inspection cycle of a vehicle. Instead, the non-woven material is not just drying the case but managing the climate, and does not need regular replacement. Tests with 50 climate However, the exact energy levels are different for all the platforms. This leads to load cases with a big object at low velocity at 90o, and a small object at high speed at another angle. Development work is looking at ways to compare big drop tests to smaller lab tests and still get a reliable result. This is important, as testing big panels with a big tower requires a test institute, which is costly and takes up considerable time to do the testing. Matching lab tests to the large-scale performance of a material gives designers more flexibility for case development. The test conditions are also simulated and matched against the test results using tools such as LSDyna and Abaqus. Vehicle designers also do their own simulation and integrate the simulation models of the materials into larger crash models of the car. Water and humidity There is a growing demand for materials to address liquid absorption in a battery case. Most engineers are not really aware of this issue and those of corrosion that are already appearing in cases. While this is driving the use of composite materials, it is also driving the adoption of absorbent materials, as some engineers are not aware that the membranes they use allow water vapour through and can build up on the cooling plate, leading to corrosion. Water from the air is only one source though. One case design had an issue with the cooling system, where the developers were worried about a Focus | Battery case materials This non-woven material for absorbing liquid in a battery is covered in superabsorbent particles (Courtesy of Freudenberg) May/June 2023 | E-Mobility Engineering